gc: fix untargeted projects being deleted

`delete_unused_projects` needs a full list of active projects to figure
out which orphaned .git dirs need to be deleted. Otherwise it thinks
that only the projects specified in args are active.

Bug: 447626164
Change-Id: I02beebf6a01c77742a8db78221452d71cd78ea73
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/550061
Tested-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>

tests/test_subcmds_gc.py

@@ -0,0 +1,82 @@
+# Copyright (C) 2026 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittests for the subcmds/gc.py module."""
+
+import unittest
+from unittest import mock
+
+from subcmds import gc
+
+
+class GcCommand(unittest.TestCase):
+    """Tests for gc command."""
+
+    def setUp(self):
+        self.cmd = gc.Gc()
+        self.opt, self.args = self.cmd.OptionParser.parse_args([])
+        self.opt.this_manifest_only = False
+        self.opt.repack = False
+
+        self.mock_get_projects = mock.patch.object(
+            self.cmd, "GetProjects"
+        ).start()
+
+        self.mock_delete = mock.patch.object(
+            self.cmd, "delete_unused_projects", return_value=0
+        ).start()
+
+        self.mock_repack = mock.patch.object(
+            self.cmd, "repack_projects", return_value=0
+        ).start()
+
+    def tearDown(self):
+        mock.patch.stopall()
+
+    def test_gc_no_args(self):
+        """Test gc without specific projects."""
+        self.mock_get_projects.return_value = ["all_projects"]
+
+        self.cmd.Execute(self.opt, [])
+
+        self.mock_get_projects.assert_called_once_with([], all_manifests=True)
+        self.mock_delete.assert_called_once_with(["all_projects"], self.opt)
+        self.mock_repack.assert_not_called()
+
+    def test_gc_with_args(self):
+        """Test gc with specific projects uses all_projects for delete."""
+        self.mock_get_projects.side_effect = [["projA"], ["all_projects"]]
+        self.opt.repack = True
+
+        self.cmd.Execute(self.opt, ["projA"])
+
+        self.mock_get_projects.assert_has_calls(
+            [
+                mock.call(["projA"], all_manifests=True),
+                mock.call([], all_manifests=True),
+            ]
+        )
+
+        self.mock_delete.assert_called_once_with(["all_projects"], self.opt)
+        self.mock_repack.assert_called_once_with(["projA"], self.opt)
+
+    def test_gc_exit_on_delete_failure(self):
+        """Test gc exits if delete_unused_projects fails."""
+        self.mock_get_projects.return_value = ["all_projects"]
+        self.mock_delete.return_value = 1
+        self.opt.repack = True
+
+        ret = self.cmd.Execute(self.opt, [])
+        self.assertEqual(ret, 1)
+        self.mock_repack.assert_not_called()